System and method for separating a trace element from a liquid hydrocarbon feed

ABSTRACT

The present invention is generally directed to removing a trace element from a liquid hydrocarbon feed. The liquid hydrocarbon feed, containing the trace element, is mixed with the water along with a hydrocarbon-soluble additive. While being mixed, a compound, which in some cases is preferably insoluble, is formed by the hydrocarbon-soluble additive chemically reacting with the trace element. A phase separation device, such as a desalter or an oil-water separator, receives the oil-water emulsion containing the compound and resolves the mixture to produce the compound, effluent brine, and effluent liquid hydrocarbon with a reduced concentration of the trace element as compared to the liquid hydrocarbon feed. In some embodiments, the present invention is directed to removing elemental mercury from a liquid hydrocarbon feed. A hydrocarbon-soluble sulfur-containing additive, typically an organic polysulfide, is mixed with the liquid hydrocarbon feed and water. The hydrocarbon-soluble, sulfur-containing additive reacts with the mercury, rapidly forming an agglomeration of mercuric sulfide which is then dispensed with the effluent brine or the effluent liquid hydrocarbon.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part of U.S. patent applicationSer. No. 12/132,475 filed Jun. 3, 2008, which is hereby incorporatedherein in its entirety by reference.

TECHNICAL FIELD

This invention relates generally to separating a trace element from aliquid hydrocarbon feed within a phase separation device, such as adesalting unit or oil-water separator.

BACKGROUND OF THE INVENTION

Liquid hydrocarbon feeds generally contain an assortment of traceelements in amounts generally ranging from several parts per billion(ppb) to several thousand ppb depending on the feed source. Theseelements often cause corrosion within equipment and may deteriorate orpoison a catalyst of a subsequent treatment process. For example,mercury may amalgamate with a surface metal, such as copper or aluminum,collecting with time in piping, valves and even in larger structuressuch as fractional distillation columns. Equipment replacement orabstraction of this deleterious metal from the equipment can be veryexpensive and potentially hazardous. Therefore, it may be preferable toremove the trace elements as early as possible during processing, suchas removal prior to distillation of the feed or even while still at thehydrocarbon recovery site. However, due to the liquid hydrocarbon stateof the feed prior to distillation being more chemically complex, currenttechnologies for removing the trace elements prior to hydrocarbondistillation tend to be less developed.

Various successful methods for removal of trace metal contaminateswithin liquid hydrocarbon feed prior to fractional distillation havenonetheless been developed. For example, U.S. Pat. No. 6,350,372 B1discloses utilizing a solubilized sulfur compound in combination with anabsorbent carrier. In particular, a liquid hydrocarbon feed is mixedwith a miscible sulfur compound and then placed in contact with a fixedbed absorbent, thus removing at least 85% of the mercury on an elementalbasis. U.S. Pat. No. 4,474,896 claims the use of absorbent compositions,mainly polysulfide based, for removal of elemental mercury from gaseousand liquid hydrocarbon streams. Specifically, the absorbent compositionscomprise a polysulfide, a support material and metal cation capable offorming an insoluble metal polysulfide. While the approach of usingfixed bed absorbents to extract trace elements, including mercury, froma hydrocarbon feed have shown to be successful, they also include anumber of less than desirable attributes. Absorbent beds tend to getclogged by solid particulates in the crude, thus impeding the flow ofthe feed. Absorbents can also be very costly due to the large quantityneeded, especially if there is a high concentration of the trace elementor elements being extracted. In addition, stripping the absorbent isgenerally necessary prior to disposal or recycling of the absorbent.

Another method to remove mercury from liquid hydrocarbon condensate isdisclosed in U.S. Pat. No. 4,915,818. In this method, the use ofabsorbent carriers is eliminated by treating the liquid hydrocarbonswith a dilute aqueous solution of alkali metal sulfide salt. Due to thehigh partition coefficient of the sulfur compounds in the aqueous phase,the risk of contaminating the liquid hydrocarbons with sulfur islimited. However, while this process minimizes the risk of sulfurcontamination, mercury present in the organic phase may also be lesslikely to react to the alkali metal sulfide salt as its chemicaldependency may be governed by the phase it resides in. In particular,the organic mercury compounds are soluble in the liquid hydrocarbon feedand typically are far less reactive than elemental mercury or inorganicmercury compounds.

In view of the foregoing, previous methods of trace element removal areconsidered less than desirable and new methods of overcoming theproblems associated with trace element extraction from hydrocarbon feedwould be extremely useful.

SUMMARY OF THE INVENTION

The present invention comprises removing a trace element from a liquidhydrocarbon, such as crude oil, natural gas, and other petroleumproducts. The liquid hydrocarbon is mixed or emulsified with water and ahydrocarbon-soluble additive. During mixing, the additive chemicallyreacts with the trace element forming a compound. This compound istypically an aqueous insoluble compound, such that the compound mayeasily be separated and removed in subsequent treatment processes. Aphase separation device, such as a desalter or an oil-water separator,resolves, i.e., separates, the oil-water emulsion containing thecompound. The resolved mixture produces the compound formed by mixingthe additive with the trace element, effluent brine, and effluent liquidhydrocarbon with a reduced concentration of the trace element ascompared to the liquid hydrocarbon feed. The compound may be dispensedfrom the phase separation device with the effluent brine or the effluentliquid hydrocarbon and may later be filtered out.

In some embodiments, the present invention is directed to removingelemental mercury from a liquid hydrocarbon feed. A sulfur-containinghydrocarbon-soluble additive is mixed with the liquid hydrocarbon feedand water to produce an emulsified solution. In some instances, theliquid hydrocarbon is already emulsified with the water prior toinjection of the additive and in other scenarios the additive may beadded directly to either the liquid hydrocarbon or water and then canall be mixed together. For instance, an organic polysulfide can beinjected directly into the liquid hydrocarbon stream prior to beingemulsified with water or it can be injected into an emulsified oil-watermixture. Regardless of the mixing strategy, the sulfur-containingadditive reacts with the mercury, concentrated within the liquidhydrocarbon, rapidly forming an agglomeration of mercuric sulfide whichis then dispensed with the effluent brine or the effluent liquidhydrocarbon for subsequent filtering.

According to one embodiment of the present invention, a system isemployed to remove a trace element from a liquid hydrocarbon. The systemincludes first and second fluid lines fluidly communicating with a phaseseparation device. In a refinery setting, where the phase separationdevice may comprise a desalting unit, the first fluid line can contain aliquid hydrocarbon feed and the second fluid line can contain washwater. A hydrocarbon-soluble additive can be mixed with either theliquid hydrocarbon feed or the wash water, such that it chemicallyreacts with the trace element as the fluids are emulsified. The fluidmixture is then resolved within the phase separation device producingeffluent liquid hydrocarbons with a reduced concentration of the traceelement that can be dispensed through a first output line, effluentbrine that can be dispensed through a second output line, and thecompound formed by mixing the additive with the trace element, which canbe dispensed from the phase separation device with either of theeffluent brine or the effluent liquid hydrocarbon. If the trace elementis removed at the hydrocarbon recovery site, such as an offshoreplatform, the phase separation device may comprise an oil-waterseparator. Here, the first fluid line can contain a contaminatedoil-in-water mixture and the second fluid line can contain ahydrocarbon-soluble additive that can be directly injected into thefirst fluid line to treat the mixture. As the additive is mixed with thecontaminated oil-in-water mixture, the additive chemically reacts withthe contaminant or trace element forming a compound. As the mixture isseparated, the liquid hydrocarbon is recovered such that it has areduced concentration of the trace element.

The above mentioned and other features of this invention will becomemore apparent and better understood by reference to the followingdetailed description taken in conjunction with the accompanyingdrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a flow chart depicting steps for removing trace elements fromliquid hydrocarbon feed, according to one embodiment of the presentinvention.

FIG. 2 is a schematic diagram depicting a system for removing traceelements from liquid hydrocarbon feed, according to one embodiment ofthe present invention.

FIG. 3 is a schematic diagram depicting a system for removing traceelements from liquid hydrocarbon feed, according to one embodiment ofthe present invention.

The figures are not necessarily to scale and certain features may beexaggerated in order to better illustrate and explain the presentinvention. Similarly, the figures have been simplified from a processingstandpoint to exclude certain types of equipment, such as mixingdevices, not essential for understanding the invention by one skilled inthe art.

DETAILED DESCRIPTION OF THE INVENTION

Hydrocarbon feeds, generally a conglomeration of hydrocarbon chains withapproximate lengths ranging between C₅H₁₂ and C₄₂H₈₆, typically containa variety of trace elements. The trace elements range from alkalineearth metals, transition metals, post-transition metals, and nonmetalsand generally consist of calcium (Ca), vanadium (V), chromium (Cr), iron(Fe), cobalt (Co), nickel (Ni), copper (Cu), zinc (Zn), arsenic (As),selenium (Se), molybdenum (Mo), cadmium (Cd), indium (In), tin (Sn),antimony (Sb), tellurium (Te), barium (Ba), mercury (Hg), thallium (Tl),lead (Pb), and/or bismuth (Bi). For various reasons, including corrosionprevention and ensuring environmental sustainability, it is oftendesirable to extract one or more of these trace elements during initialtreatment of the feed.

FIG. 1 depicts steps, according to one method of the present invention,for removal of a trace element from a liquid hydrocarbon. First, asshown in step 10, a hydrocarbon-soluble additive is mixed with a liquidhydrocarbon having a concentration of a trace element and with water. Asthese fluids are mixed, the hydrocarbon-soluble additive chemicallyreacts with the trace element forming a compound. Typically, thiscompound will be insoluble in both the hydrocarbon and aqueous phase sothat it may easily be removed during future processing. Once theoil-water emulsion containing the compound is formed, it is resolvedinto phases in a phase separation device, as shown in step 20. Theeffluent phases are then dispensed separately from the phase separationdevice, as depicted in step 30. The compound formed by thehydrocarbon-soluble additive chemically reacting with the trace elementis dispensed along with the effluent phases. The compound then caneasily be extracted out of the effluent, as shown in step 40. Therefore,once this process has been completed, the effluent liquid hydrocarbonthat is dispensed from the phase separation device has a reducedconcentration of the trace element. Note that the “concentration of thetrace element” as used herein, is meant to describe the concentration ofthe trace element within the liquid hydrocarbon when it is in anelemental state; that is, disregarding the content of the trace elementonce it has chemically reacted with the additive or when it is in acompound state.

In certain embodiments, mercury is the trace element targeted forextraction and a hydrocarbon-soluble additive, such as an organicpolysulfide such as Di-Tertiary-Nonyl Polysulfide (TNPS), is utilized toform a compound with the mercury. The hydrocarbon-soluble sulfur-basedadditive reacts with the mercury rapidly forming an agglomeration ofmercuric sulfide through the following reaction:

R—S—S_(x)—S—R+XHg→R—S—S—R+XHgS

where R is any hydrocarbon or hydrogen, S is Sulfur, and X and x are thesame whole number, typically between 3 and 8. As an inorganic salt,mercuric sulfide has essentially no vapor pressure and with theconversion to an ionic salt, makes the mercury more readily availablefor removal by various techniques already known in the art. In someinstances, mercurous sulfide may also be formed from the reaction of thesulfur-based additive with the mercury in the liquid hydrocarbon feed.

FIG. 2 depicts a schematic flow process, according to one embodiment ofthe present invention, for removing trace elements from liquidhydrocarbon feed, such as in an oil refinery setting. Treatment system100 includes liquid hydrocarbon feed, commonly referred to as petroleumor crude oil, which is routed via piping 104 from storage container 102.The feed is then heated in a furnace 106 to a temperature above itsboiling point, typically ranging from about 500 to 600 degrees Celsius.The heated liquid hydrocarbon feed continues within piping 104 and ahydrocarbon-soluble additive is introduced to the liquid hydrocarbonfeed through line 108. The liquid hydrocarbon feed andhydrocarbon-soluble additive are then inputted into a phase separationdevice 110, such as a desalting unit or desalter, and blended with washwater introduced through line 112 to form an emulsion within the phaseseparation device 110. To obtain an adequate emulsion the mixture may bepassed through a pressure reducing valve (not shown) or stirred by amixing device (not shown). Alternatively, line 112, containing the washwater, may be injected directly into piping 104 upstream of the phaseseparation device 110. Similarly, the hydrocarbon-soluble additive canbe injected through the same line as the wash water and only one oflines 108 and 112 will be present. While the mixture is emulsifying, thehydrocarbon-soluble additive reacts with one or more trace elementsforming compounds, typically insoluble inorganic compounds. Resolvingthe emulsified solution produces the compound that is formed by areaction between the hydrocarbon-soluble additive with the traceelement, effluent brine, and effluent liquid hydrocarbons with a reducedconcentration of the trace element as compared to the liquid hydrocarbonfeed. As discussed later in more detail, the phase separation device 110may utilize a plurality of baffles 118, a plurality of electrodes (notshown) that create an electric field, and/or a demulsifying agent toassist in separating the mixture into phases. Additionally, a settlingagent may similarly be utilized to accelerate the settling of thecompound within the hydrocarbon and/or aqueous phase.

Once separated, the effluent brine flows out of the desalter though afirst output 114 and typically is filtered and recycled back throughline 112 as wash water. The effluent liquid hydrocarbon is dispensedfrom the phase separation device 110 into piping 116 and is transportedto fractional distillation column 120. Fractional distillation column120 is comprised of a plurality of spaced plates 122 filled withmultiple apertures 124. As the heated effluent hydrocarbon enters thefractional distillation column 120, it separates such that thehydrocarbon vapors continually ascend passing through the apertures 124within the spaced plates 122. As the hydrocarbon vapors climb in thefractional distillation column 120, they cool down and begin to condenseforming liquid fractions that are caught in the plurality of spacedplates 122. Vapors that pass all the way to the top of the fractionaldistillation column 120 exit through output 126. These vapors aretypically very light hydrocarbons and are commonly called naphtha.Heavier hydrocarbons fractions such as gasoline, kerosene, diesel,lubricating oil and heavy gas oil are dispensed through outputs 128 eachcorresponding to the spaced plates 122 within the fractionaldistillation column 120. The heaviest hydrocarbon chains collect in thebottom of the fractional distillation column 120 and are dispensedthrough output 130. These hydrocarbons are commonly referred to as theresidual. Depending on the respective output 126, 128, 130, thefractions may pass to subsequent condensers, which cool them further,and then go to storage tanks or be routed to other areas for furtherchemical processing. For instance, the naphtha dispensed from the top ofthe fractional distillation column may further be separated into lightends, such as liquefied natural gases, and heavier or denser ends. Thecompound formed by a reaction between the hydrocarbon-soluble additivewith the trace element is dispensed along with the effluent brine oreffluent liquid hydrocarbon. Conversion of the trace element to acompound makes it more available for subsequent removal throughtechniques such as filtration, coagulation, flotation, co-precipitation,ion exchange, reverse osmosis, ultra filtration and other typicaltreatment processes known in the art.

As previously mentioned, the phase separation device 110 may utilizevarious separation items, already known in the art, to assist inseparating the mixture into phases. For example and as shown in FIG. 2,a plurality of baffles 118 are contained within the phase separationdevice 110 to assist in separating the emulsified solution into phases.As illustrated in FIG. 2, a series of horizontally spaced baffles areutilized, however, any directional and spatial arrangement of thebaffles may be utilized. Similarly, the phase separation device 110 caninclude a series of charged plates or electrodes (not shown) thatoperate at relatively high voltages to create an electric field andassist in demulsifying the wash water and the liquid hydrocarbon. Thecharged plates or electrodes comprise any arrangement of anodes andcathodes disposed to create a sufficient electric field for breaking theemulsified mixture into an aqueous phase and an oil phase. A chemicaldemulsifying agent may be additionally added to the phase separationdevice 110 to aid with phase separation. The separated aqueous phasetypically consists of effluent brine that flows out of the desalterthough first output 114 and can be filtered and recycled back throughline 112 as wash water. The oil phase typically consists of effluentliquid hydrocarbons that are dispensed into piping 116 and aretransported to fractional distillation column 120. Additionally thecompound formed from the reaction of the hydrocarbon-soluble additivewith the trace element is produced and dispensed along with either ofthe effluent brine or effluent liquid hydrocarbon. Again, conversion ofthe trace element to a compound form provides increased opportunity forsubsequent removal, as the compound is larger in size than that traceelement, has an increased mass, and is typically more stabile. Achemical settling agent may be utilized to accelerate the settling ofthe compound mixed with the hydrocarbon and/or aqueous phase. Dependingon the type of settling agent, the settling agent can be added to theliquid hydrocarbon directly with the hydrocarbon-soluble additive, alongwith the wash water, or through a separate injection port upstream ordirectly into the phase separation device. Additionally, it could beadded downstream of the phase separation device directly to either theeffluent brine or hydrocarbon. Types of settling agents that may beutilized, are known in that art, and are similar to those characterizedin U.S. Pat. Nos. 7,204,927, 7,048,847, 5,681,451, 5,593572, 5,481,059and 5,476988.

FIG. 3 depicts a schematic flow process, according to another embodimentof the present invention, for removing trace elements from liquidhydrocarbon feed, such as at a hydrocarbon recovery site. Treatmentsystem 200 includes recovered contaminated hydrocarbons from reservoir202 and routed via piping 204. The recovered hydrocarbons from thereservoir 202 are normally extracted in an emulsion form and comprise anadmixture of hydrocarbons with water. The recovered hydrocarbons passthrough piping 204 and a hydrocarbon-soluble additive is injected intopiping 204 through line 206. To obtain adequate mixing with theadditive, a pressure reducing valve (not shown) or mixing device (notshown) may be employed. As the additive is sufficiently mixed with theemulsion, the additive chemically reacts with the trace element, whichcontaminates the recovered hydrocarbons, to form compounds. Again, thesecompounds can be insoluble such that they can easily be separated insubsequent processes. The mixture is then passed through phaseseparation device 210, also known as an oil-water separator, to resolvethe emulsion. Similar to the phase separation device 110, phaseseparation device 210 may also utilize baffles 216, charged plates (notshown), electrodes (not shown), a demulsifying agent, and/or a settlingagent to assist in separation of the phases and/or the compound. It canbe appreciated by one skilled in the art that neither phase separationdevice 110 nor phase separation device 210 require such items, and thatthey are only utilized to expedite the settling time of the emulsifiedmixture and the compound. Once the mixture has been resolved, thetreated liquid hydrocarbon, with reduced contamination of the traceelement, passes through line 214 to storage tank 220 where it can betransferred to another operation facility, such as the system shown inFIG. 2. The separated aqueous phase is dispensed through outlet line212. This produced water may still contain an oily residue and/or othercontaminates, and therefore, may pass through another phase separationdevice (not shown) before being recycled or disposed of. In this case, asimilar process may be repeated such that the produced water is injectedwith an additive prior to passing through the separation device suchthat additional contaminates are removed.

1. EXAMPLES

The following example shows how mercury content is reduced from a liquidhydrocarbon feed to minimal levels, according to the present invention.Test results were taken at a plurality of locations, each correspondingto a different stage within a liquid hydrocarbon treatment facility,over four hour intervals to measure the variation in the concentrationof mercury within a contaminated liquid hydrocarbon feed. As shown inFIG. 2, Point A is located upstream of phase separation device 110 andin this example upstream of where the hydrocarbon-soluble additive isinjected through line 108, Point B is located downstream of the phaseseparation device on first output 114, Point C is located downstream ofthe phase separation device on second output 116, Point D is located onoutput 130 of fractional distillation column 120, and Point E is locatedon output 126 of fractional distillation column 120.

Time Point A Point B Point C Point D Point E (Hours) (ppb) (ppb) (ppb)(ppb) (ppb) 0 109.4 13.2 376.2 0 452.4 4 60.7 8.6 201.9 1 748.2 8 82.513.2 140.4 2.2 127.3 12 103 14.2 281.8 1.8 2.6 16 17.7 6.8 102 2 7.6 20170.6 11.5 259.9 2.8 13.2 24 187.3 8.8 246.6 0.2 7.1The results above indicate that after the hydrocarbon-soluble additivewas injected into the liquid hydrocarbon feed, the mercury concentrationbegan to taper off significantly and stabilize by the twelfth hour oftesting to a level of less than 15 ppb at point E, which is locateddownstream of the phase separation device 110 on output 126 offractional distillation column 120. A more immediate drop at Point E maybe realized through proper flushing of the equipment prior to commencingthe injection of the additive. While no significant change may be seenat Point B in this example, a settling agent can be used, e.g., byinjecting the settling agent at either Points 108 or 112, to promote anincrease of mercury concentration in the effluent brine. Consideringthat a concentration of mercury is continually detected at Point C, itappears that the compound is carried by the effluent liquid hydrocarbonto the distillation chamber. Note that in this example, detection doesnot speciate and therefore, the readings include the total mercuryconcentration present in both an elemental and compound state. It iscontemplated that the compound may have collected at the bottom of thedistillation chamber, as an increased concentration was not detected atPoint D, while a significant drop did occur at point E.

2. DEFINITIONS

Certain terms are defined throughout this description as they are firstused, while certain other terms used in this description are definedbelow:

The term “sulfur-based” as used herein means any compound containing oneor more sulfur atoms.

The term “mercury salt” as used herein means any chemical compoundformed by replacing all or part of the hydrogen ions of an acid with oneor more mercury ions.

The term “mercury sulfide” as used herein means mercuric sulfide,mercurous sulfide, or a mixture thereof. Normally the mercury sulfide ispresent as mercuric sulfide and thus the stoichiometric equivalent wouldbe one mole of sulfide ion per mole of mercury ion.

The term “organic polysulfide” as used herein means any chemicalcompound containing two or more sulfur atoms bonded to any hydrocarbonor hydrogen atom.

The unit “ppb” as used herein means parts per billion.

The term “oil-water” as used herein means any mixture comprising aliquid hydrocarbon with water. Therefore, it is to be understood thatthe term “oil-water” is inclusive of both oil-in-water emulsions andwater-in-oil emulsions.

While this invention has been described as having an exemplary design,the present invention may be further modified within the spirit andscope of this disclosure. This application is therefore intended tocover any variations, uses, or adaptations of the invention using itsgeneral principles. Those skilled in the art will appreciate that theabove described embodiments are merely illustrative of the presentinvention and that many variations of the above described embodimentscan be devised without departing from the scope of the invention. Forinstance, it is contemplated that the hydrocarbon-soluble additive canbe introduced into the liquid hydrocarbon or oil-water mixture throughmultiple injection points as compared to a single injection line. It istherefore intended that such departures from the present disclosure,that come within the known customary practice in the art to which thisinvention pertains, be included within the scope of the followingappended claims and their equivalents.

1. A method for removing a trace element from a liquid hydrocarboncomprising: (a) mixing a liquid hydrocarbon having a first concentrationof a trace element, water, and a hydrocarbon-soluble additive to producean oil-water emulsion containing a compound, the compound formed by thehydrocarbon-soluble additive chemically reacting with the trace element;and (b) resolving the oil-water emulsion in a phase separation device toproduce an effluent brine and an effluent liquid hydrocarbon having asecond concentration of the trace element, the second concentrationbeing less than the first concentration.
 2. The method of claim 1,wherein the compound is dispensed from the phase separation device withat least one of the effluent brine and the effluent liquid hydrocarbon.3. The method of claim 1, wherein the trace element is selected from agroup consisting of mercury, vanadium, chromium, iron, cobalt, nickel,copper, zinc, arsenic, selenium, molybdenum, cadmium, tin, antimony,thallium, and lead.
 4. The method of claim 1, wherein the phaseseparation device is selected from a group consisting of a desaltingunit and an oil-water separator.
 5. The method of claim 1, wherein thestep of mixing comprises mixing the hydrocarbon-soluble additive with atleast one of the liquid hydrocarbon and the water before the liquidhydrocarbon and the water are mixed to produce the oil-water emulsion.6. The method of claim 1, wherein the mixing step comprises adding thehydrocarbon-soluble additive to the oil-water emulsion after the liquidhydrocarbon and the water are mixed.
 7. A method for processing a liquidhydrocarbon comprising: (a) providing a liquid hydrocarbon feed with afirst concentration of a trace element; (b) providing ahydrocarbon-soluble additive that is configured to chemically react withthe trace element to form a compound; (c) providing a wash water; (d)mixing the liquid hydrocarbon feed, the hydrocarbon-soluble additive,and the wash water to form an emulsion containing the compound formed bymixing and reacting the trace element with the hydrocarbon-solubleadditive; and (e) resolving the emulsion in a phase separation device toobtain an effluent brine and an effluent liquid hydrocarbon with asecond concentration of the trace element, the second concentrationbeing less than the first concentration.
 8. The method of claim 7,further comprising dispensing the compound from the phase separationdevice in a mixture with at least one of the effluent brine and theeffluent liquid hydrocarbon.
 9. The method of claim 7, wherein the phaseseparation device is selected from a group consisting of a desaltingunit and an oil-water separator.
 10. The method of claim 7, wherein thetrace element is selected from a group consisting of mercury, vanadium,chromium, iron, cobalt, nickel, copper, zinc, arsenic, selenium,molybdenum, cadmium, tin, antimony, thallium, and lead.
 11. A method forremoving mercury from a liquid hydrocarbon comprising: (a) mixing aliquid hydrocarbon having a first concentration of mercury, water, and ahydrocarbon-soluble additive to produce an oil-water emulsion containinga mercury salt, the mercury salt formed by the additive chemicallyreacting with the mercury; and (b) resolving the oil-water emulsion in aphase separation device to produce an effluent brine and an effluentliquid hydrocarbon having a second concentration of mercury, the secondconcentration being less than the first concentration.
 12. The method ofclaim 11, wherein the hydrocarbon-soluble additive is sulfur-based andthe mercury salt is mercury sulfide.
 13. The method of claim 11, whereinthe hydrocarbon-soluble additive is an organic polysulfide.
 14. Themethod of claim 11, wherein the phase separation device is selected froma group consisting of a desalting unit and an oil-water separator.
 15. Asystem for treatment of a fluid comprising: a first feed line containinga first fluid having a first concentration of a trace element; a secondfeed line containing a second fluid; a phase separation device in fluidcommunication with the first feed line and the second feed line, thephase separation device configured to separate at least portion of amixture comprised of the first fluid and the second fluid; and a firstoutput line connected to the phase separation device configured todispense a third fluid from the phase separation device with a secondconcentration of the trace element, the second concentration being lessthan the first concentration.
 16. The system of claim 15, wherein: thephase separation device is a desalting unit; the first fluid is a liquidhydrocarbon feed; the second fluid is a wash water; the third fluid isan effluent liquid hydrocarbon feed; and further comprising a secondoutput line that is directly connected to the desalting unit configuredto dispense an effluent brine.
 17. The system of claim 16, wherein: atleast one of the first and second feed lines is configured to receive ahydrocarbon-soluble additive with at least one of the liquid hydrocarbonfeed and the wash water, such that the hydrocarbon-soluble additive isconfigured to chemically react with the trace element to produce acompound; and the desalting unit is configured to dispense the compoundwith at least one of the effluent brine and the effluent liquidhydrocarbon.
 18. The system of claim 15, wherein: the phase separationdevice comprises an oil-water separator; the first fluid is an oil-watermixture; the second fluid is a hydrocarbon-soluble additive configuredto chemically react with the trace element to produce a compound; andthe third fluid is an effluent liquid hydrocarbon.
 19. The system ofclaim 15, wherein the phase separation device further includes at leastone separation item, the separation item being selected from a groupconsisting of a plurality of baffles, a plurality of electrodesconfigured to create an electric field, a demulsifying agent, and asettling agent.
 20. The system of claim 15, wherein the trace element isselected from a group consisting of mercury, vanadium, chromium, iron,cobalt, nickel, copper, zinc, arsenic, selenium, molybdenum, cadmium,tin, antimony, thallium, and lead.